Link building service
State Factory offer an external Link building service
Identifying sites you would like to link to you is time consuming but important as it forces you to think about horizontal and vertical markets that could benefit from linking to your site, and of course you could benefit from. A good example is the one I gave above, having an insurance web site that provides insurance for health, home, car, travel etc. should be looking for links in each of these areas. Searching for the sites at the top of the search engine rankings is a good way to start, list the ones that you feel could benefit from your web site and that could generate targeted traffic to your site. Once you have listed them order them in importance and contact them!
An extension to contacting relevant markets is to provide an affiliate service to those web sites. An affiliate is one that benefits from a visitor to their site being sent to yours and converted into a sale. This benefit is usually monetary, either fixed cost or a percentage of the sale. This type of partnership enforces the other web site to market yours effectively to their visitors has they are interested in earning more revenue.
Natural links occur when your content is worth linking to. This is the most important part of link building, great content! Providing a visitor to great relevant unique content will ensure they re-visit your site and possibly forward your web site on to others. A good way to create these natural links is to write articles for your market domain, such as this one (yes shameless I know). Well written articles that are syndicated to other web sites, web users etc. will naturally gain new visitors to your site.
Actively getting involved in your market domains online community is a good way to get links and traffic to your site, being a member of the forums allows you to meet people interested in your services and when you post you can have a link to your web site in your signature.